Well, I really like GO but it at the same time I hate it because it miss many things: trade, PvP... and the most important thing a good story. For now you simply go and catch 1500 Rattata/Pidgey (now some of them replaced with Sentret) and nothing else... and we rural players have many problems playing because there isn't many PokéStops....
About Duel... I hate that the boosters are random but I like it because it has an interesting story (not finished for now ) and you can play it without many problems.
With this, I have to say that for now I like Duel much more